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  3. Living near airports might not only lead to residents suffering sleepless nights—they could also have terrible weather, scientis

Living near airports might not only lead to residents suffering sleepless nights—they could also have terrible weather, scientis

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问题     Living near airports might not only lead to residents suffering sleepless nights—they could also have terrible weather, scientists say. For aircraft increase the chances of snow and rain when they take off and land, an extraordinary study suggests.
    Apparently the effects of jet planes punching through clouds are similar to "cloud seeding" operations, where ice crystal are created in the atmosphere to make it rain.
    The findings—published in the respected academic journal Science—are based on satellite images of clouds around airports and computer models of cloud behavior. The side-effect of flying is likely to be the most obvious around the world’s busiest airports, such as Heathrow where more than 1,200 planes land or take off every day.
    The phenomenon occurs when aircraft smash through clouds containing "super-cooled" water or water that exists as droplets of liquid at temperatures of minus 10°C or below. As an aero plane passes quickly through a cloud, the air behind the wings and propellers expands and cools quickly. These sudden drops in temperature can be enough to freeze droplets of super-cooled water—turning them into a stream of ice crystal.
    Over time, ice crystals grow and affect neighboring drops of water, creating a hole in the cloud that expands for several hours and increases the chances of snow or rain on the ground underneath.
    Dr Andrew Heymsfield, of the National Center for atmospheric Research in Boulder, Colorado, said aircraft increased the chances of snow when they punched holes in clouds after taking off and when they created "canals" in clouds when descending. "Whether an airplane creates a hole or a canal in the clouds depends on its trajectory," he said. When they climb through a super-cooled cloud layer, they can just produce a hole. But when they fly level through the cloud layer, they can produce long canals."
    The study found that super-cooled cloud layers are found with 62 miles of the world’ s major airports at least five per cent of the time. The cloud seeding effects are more noticeablely closer to the north and south poles. The researchers looked at 20 satellite images of cloud cover with holes suspended over Texas on one day in January 2007. Some of the holes were visible for more than four hours and grew more than 60 miles long.
    The team then looked at flight data from the US Federal Aviation Administration to find out what aircraft had flown in each area, between 4.3 and five miles high, on that way. They discovered that a range of aircrafts can produce holes including jumbo jets, military planes and private single engine jets.
    The researchers say it is unlikely that aircrafts affect the global climate. However, it may increase the need to de-ice planes more often in the future, they say. It’s not the first time scientists have linked aircraft to weather.
What is the essential that determine a hole or a canal in the cloud created by an airplane?
选项 A、The temperature around the airplane in the cloud.
B、The trajectory that an airplane flies.
C、The height of the airplane when it is flying.
D、The thickness of the cloud which an airplane flies through.
答案B
解析 细节题。根据题目中determine a hole or a canal可定位至文章第六段．根据第六段 “Whether an airplane creates a hole or a canal in the clouds depends on itstrajectory，”(“一架飞机是否在云层中制造孔洞或沟槽，取决于其飞行轨道”)可见飞机飞行轨道决定了其是否会制造孔洞或沟槽，因此选择B项。
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